Adjustable telescoping transformer with a loop core



June 15, 1954 J. A. ANDERSON 24,681,433

ADJUSTABLE TELESCOPING TRANSFORMER WITH A LOOP CORE Filed June 4, 1951 Fig; 2

Fig.3 I Fig. 4

James A. Anderson INVENTOR.

itlome Patented June 15, 1954 UNITED STATES 3 Claims.

This invention relates to adjustable transformers for alternating current load circuits of all types and, although not limited to this type, the invention is especially suitable for transformers used in arc welding circuits. The invention is more specifically related to regulating transformers of the induction type in which the current drawn from the secondary winding of the transformer may be controlled by controlling the ratio of transformation.

The main object of the invention consists in providing a transformer of the induction type with a wide range of regulability of the secondary current and of great simplicity of construction in which the transformer ratio may be adjusted with high precision.

A further principal object of the invention consists in using a closed transformer core or frame without gap or interruption and without auxiliary structure for the purpose above mentioned.

Transformers permitting fine regulation and more specifically transformers of this type which are used for arc welding are most frequently of the reluctance type in which thedesired regulation is obtained by a change in the magnetic reluctance of the transformer core or of adjoining auxiliary structures. In these constructions the magnetic flux passing through the; transformer core also passes through an adjustable gap the width of which regulates the reluctance of the magnetic circuit. Alternatively the reluctance may be varied by means of variable magnetic shunts or by means of variable auxiliary magnetic circuits. This type of transformer, however, does not have a wide range of adjustability. Moreover the transformers of this type usually have a rather involved construction, as secondary cores and other auxiliary elements have to be used and as a section of the rather heavy and bulky transformer core or frame or an auxiliary or secondary core have to be moved.

Transformers of the induction type have a much wider range of adjustability, but the known types also show a rather involved construction as they usually are provided with a counterbalanced secondary coil which is moved towards the primary coil, the latter being mounted on an auxiliary core projecting from the main transformer core in order to permit such relative motion of the secondary coil. These known constructions therefore have the disadvantage that an extraneous construction must be used for sup porting the secondary coil and for producing a swinging movement of the same towards the primary coil and moreover the core construction is usually of a complex type in order to accommodate the primary coil in a suitable position.

According to the invention the primary and secondary coils are both mounted on the same leg of a completely closed transformer frame and are moved relatively'to each other along the said leg. One of the transformer coils is provided with an annular winding of such a size that it ADJUSTABLE TELESCOPING TRANSFORMER WITH A LOOP CORE James A. Anderson, Memphis, Tenn.

Application June 4, 1951, Serial No. 229,781

permits to accommodate the other coil in its interior. Preferably only one of the coils is movable while the other coil is fixed and the movement is imparted to the movable coil by attaching it to the movable member of a helical or worm gear sliding in a direction which is parallel to the transformer leg on which the two coils are mounted. The ratio of transformation may thus be adjusted within relatively wide limits while the efficiency of the transformer remains high on account of the fact that both coils are centered on the same leg of a closed transformer and that there are therefore no stray fields which cause losses.

Further objects of the invention will be explained in detail in the following specification.

The invention is illustrated in the accompanying drawings showing one embodiment thereof by way of example. It is however to be understood that the example shown has been selected for the purpose of explaining the principle of the invention and the best mode of applying said principle and that other modes of applying the same principle can be readily designed by experts skilled in the art on the basis of the disclosure made in the specification. A departure from the example shown in the drawing is therefore not necessarily a departure from the principle of th invention.

In the drawings:

Figure 1 is an elevational view of the transformer assembly;

Figure 2 is an elevational sectional View of'the transformer assembly, the section being taken along line 2-2 of Figure 1;

Figure 3 is a sectional view of a detail, the section being taken along line 3-3 of Figure 1;

Figure 4 is a sectional view of a detail, the section being taken along line 4-4 of Figure 1.

As above explained, the transformer according to the invention, comprises a completely closed laminated core frame ll], without gap or interruption on which the primary and secondary transformer coils are directly mounted. The core It has the shape of an oblong closed frame with parallel longitudinal legs II, I 9 and with parallel transverse legs l3 joining the longitudinal legs. The primary and secondary coils l2 and I5 are mounted on the same transformer leg II and one of said coils l2 in Figure 1) may be mounted fixedly on the frame or on a support or part to which the frame is attached. This coil, in the example shown, is of a larger diameter than the other coil Hi. The spool M of the coil has a hollow interior of sufficient size to accommodate the smaller coil it? which may therefore be moved partly or completely into the space encircled by the larger coil I2.

While the lamellae of the laminated transformer core or frame may be held in the usual manner on the legs -!3 and I9 special clamping and guiding plates, indicated at 22, may be used in connection with the leg I I These plates may serve as a guide for the movable coil, the spool of which may have recesses 26 for accommodating said plates. These guiding plates will assist in producing a smooth movement of the coil without jamming.

The movable coil [5 is mountedv on a spool 24 which may be provided with the above mentioned recesses 26 which are filled by the guiding plates 22. The spool 24 carries the winding of the transformer in the conventional manner; It may be provided with flanges 24 and on one of said flanges an angular bracket I6 is fixedly mounted which carries a bolt ll passing through a bore insaid angularb'racket, which bolt projects from a yoke-member i8. The yoke member is provided with parallel side plates having bores through which a shaft 341 may pass. This shaft is either a square shaft or may be a round shaft provided with a key 32. Within the yoke and between the side plates of the same a worm wheel is arranged which is mounted on said shaft 30 and which is secured on said shaft by means of thekey 32 so that it is rotated with the shaft. Preferably, the worm wheel fits into the space between the two side plates of the yoke member l8 and it is thus axially held within said yoke member.

The worm wheel. meshes with a rack 33 which is mounted on the inside of the leg 19 of the transformer frame which faces the leg II. The rack 33 may be held on the leg 19 by means of clamps 34 which may also carry the bearing blocks'36 for shaft 30.

The shaft 3ll preferably is stepped so as to be axially held between'the two bearing blocks 36. The shaft is provided with an extension 38 ass ingthrough a bore 39 in the transformer leg 13. On the end of the extension 38 of the shaft 39 projecting outwardly a crank or handwheel'may be mounted which permits to rotate the worm wheel and thereby to adjust the position of the coil in a very precise manner.

Instead of the crank a pulley orsprocket wheel may be mounted on the extension 38 in order to drive the shaft 38 from some controlling mechanism;

The above described construction provides an adjustability of the coil l5 which permits to adjust the transformation ratio within rather wide limits. More specifically the coil l5 may be moved from a position in which it is completely contained within the coil l2 to a position in which'the distance between the coils is relatively large. In the position in which one coil is located within the other coil the maximum induction takes place and there is a direct inductivecooperation between the two windings of the coils to the maximum extent. When the coil 15 has been moved to a sufficient distance from the coil l2 by means of the mechanism as above described the induction between the coils is entirely eliminated and induction currents are produced solely by the variation of the magnetic flux which is produced by the primary coil. This permits a wide range of adjustability and also a high efficiency over the entire range on account of the fact that a closed transformer core frame is used.

Obviously, it does not make any difference whether the coil 15 or the coil I2 is the primary coil of the induction apparatus. Either of them may be used, the selection being determined by the number of turns, the available space and by other circumstances.

As above indicated, the transformer. may also be usedfor an automatic voltage. regulation in connection" with. one of the; well '5 known. devices which in this case may drive the shaft 30 in order to adjust the transformer for the required voltage.

Minor changes of an unessential nature, especiallychanges in the construction may be made withoutdeparting from the essence of the invention as defined in the adjoined claims.

Having described the invention, what is claimed as new is:

1. An' adjustable transformer comprising a completely closed transformer core with two parallel legs, a primary and a secondary-coil on one of said transformer legs, encircling the same, the primary coil being annular surrounding-ahollow interior space between said core and said primary coil adapted to accommodate'the secondary coil, said secondary coil being movable along said leg from a position in which one of the two coils substantially surround each other to a position in which they are at a distance from each other, a bracket attached to the smaller coil; a guiding and advancing means along the leg parallelto the coil encircled leg, means carried by said bracket for engaging said guiding and advancingmeans and further means for advancing said aforesaid meansalong said guiding and advancing means and along the transformer leg parallel to'the coil encircled leg, thus moving the movable coil along the encircled leg.

2. An adjustable transformer as claimedin claim 1, wherein said guiding and advancing means consists of a-rack attached to the leg parallel to the coil encircled leg and wherein the means engaging the aforesaid guiding and advancing means consists of a worm wheel, a rotatable shaft carrying said worm wheel and adapted to rotate the same, a yoke carrying said wormv wheel, fixed to the said bracket and means forrotating said shaft.

3. An adjustable transformer comprising a completely closed transformer core with two par allel legs, a primary and a secondary coil on one of said two parallel'legs encircling the same; the

primary coil being fixed and annular, the inner surface of said annular coil being spaced'from* the transformer core to an extent corresponding to the outer diameter of the secondary coil,

means forslidably seating and guiding said secondary coil on the leg of the "transformer core encircled by the primary coil, and means for dis- References Cited in the file of this patent UNITED. STATES PATENTS Number Name 1 Date" 516,846 Thomson Mar. 20, 1894 597,180 Gates Jan. 11, 1898 2,283,712 Welch May 19, 1942 FOREIGN PATENTS Number Country Date.

50,812 Sweden .May 27, 1920 276,529 Great Britain Sept. .1, 1927 

